An analyst note flagging a possible slowdown by Microsoft in leasing data center capacity grabbed the market's attention on Monday, lending credence to skepticism among investors worried that the AI-led stock-market boom might be running out of steam.

Update: Microsoft issued a statement to Jefferies obtained by CNBC that refuted the TD Cowen note. "The broker report may also have some misunderstanding about Microsoft's definition of leasing," the statement said.